Streamlined and unified opacity methods

Currently methods for getting/setting opacity have different workflow:

- in IE w/o opacity support `getStyle_IE` invokes `getOpacity_IE`
- in other browsers `getOpacity` invokes `getStyle` (doing unneeded operations like `normalizeStyleName('opacity')`)

Also `setOpacity_IE` and `getOpacity_IE` check `STANDARD_CSS_OPACITY_SUPPORTED` each time they are invoked (not good for animation performance).
Fixed typo in PDoc; added missing semicolon
Fix for ticket 1282

Attempt to fix https://prototype.lighthouseapp.com/projects/8886/tickets/1282-latest-prototypejs-from-github-repo-fails-in-opera

Opera (at least 11.X) has false positive result in feature test `'styleFloat' in DIV.style`, but should have its own `getStyle_Opera` and standard `setOpacity`/`getOpacity`.

Another variant:

    if (Prototype.Browser.Opera) {
      // Opera also has 'styleFloat' in DIV.style
      methods.getStyle = getStyle_Opera;
    } else if ('styleFloat' in DIV.style) {
      methods.getStyle = getStyle_IE;
    }
    if (!STANDARD_CSS_OPACITY_SUPPORTED) {
      methods.setOpacity = setOpacity_IE;
      methods.getOpacity = getOpacity_IE;
    }
getOffsetParent method fixed - bug in IE7: offsetParent sometimes returns HTML element
Memory leak fix in Prototype.
fixes issue #3284

https://prototype.lighthouseapp.com/projects/8886/tickets/3284
enumerable.js#all improved performance by removing AND operation
update sizzle CSS engine
Added compiled prototypejs

added Compiled JS and JS min files
include performance and ECMA6 detect
udpate selectors test to handle errors thrown by new Sizzle
move current tests to old_tests
new testing with Mocha and PhantomJS
added chai assertion library
update assert to use chai assert
update assert to use chai assert
not needed already included on domtests.html
missing logo on domtests.html
added DOM fixtures for tests
link to DOM Interactions and add chai